Our studies have shown that hemorrhage, without tissue trauma, produces a marked depression in cell-mediated immunity which, despite fluid resuscitation, persists for approximately 4 days. Moreover, trauma in the form of medline laparotomy (without significant blood loss) also produces marked immunodepression. However, despite the marked immunodepression following simple hemorrhage as well as following laparotomy, there was no mortality associated with either of these insults. Nonetheless, posthemorrhage animals exhibit decreased capacity to ward off septic challenge 3 days after hemorrhage. Since, in most clinical situations, hemorrhage occurs in conjunction with trauma, we developed a nonheparinized mouse model of trauma-hemorrhage and resuscitation which is associated with prolonged immunosuppression (i.e., >5 days) and results in significant mortality within 6 days postresuscitation. Our hypothesis is that mediators such as prostaglandins (e.g., PGE2), certain cytokines, and neuroendocrine components (catecholamines, glucocorticoids, endorphins- opioids) are released following trauma, as sell as following hemorrhage and they act synergistically to produce a prolonged state of immunodepression, as compared to either of these insults alone. Our specific aims are to use mouse models of trauma, hemorrhage, as well as trauma-hemorrhage and resuscitation, and determine 1) the circulating and potentially local profiles of mediators such as PGE2, catecholamines, corticosterone, endorphins, opioids (morphine and codeine) (with respect to concentration, timing, duration) and identify the mediator(s) which induces prolonged depression of cell-mediated immunity following trauma-hemorrhage; 2) alterations in Mphi and lymphocyte cellular signal transduction mechanisms (i.e., [Ca2+]i, Ca2+ fluxing, protein kinase activity, IP3, ATP and cyclic nucleotide levels) along with endogenous opioids-endorphins release; 3) gene expression of cyclooxygenase, and various lymphokines and cytokines known to have immunosuppressive and/or immunoenhancing effects, including IL-4, IL-10, and TGF-beta. We will also asses immune cell expression of heat shock protein as well as the rate of programmed cell death in both mature and immature cell populations; 4) whether decreasing Kupffer cell number by retreating the mice with gadolinium chloride prevents the increase in systemic inflammatory mediators, and maintains various immunological functions following trauma-hemorrhage in distinct cells, and improves the overall survival of animals; and 5) whether the use of immunomodulators such as Ca2+ antagonists, chemically modified heparin, chloroquine, ibuprofen, ATP-MgCl2, carnitine, as well as cytokine antibodies/inhibitors (e.g., IL-1ra, TNF binding protein) will aid in dissecting the mechanism of protracted immunosuppression. Moreover, their ability to improve survival following trauma-hemorrhage and to decrease susceptibility to subsequent sepsis will be determined. The use of biochemical, physiological, cellular and molecular biological techniques to determine the mechanism responsible for prolonged immunodepression, organ dysfunction and mortality following trauma-hemorrhage and resuscitation should provide useful information for the treatment and care of trauma victims.